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nervus phrenicus
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The phrenic nerve and its relations with the Vagus Nerve (Phrenic labeled at upper left)
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Plan of the cervical plexus (Phrenic labeled at bottom right)
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C3-C5 of Cervical Plexus
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The arises from the third, fourth, and fifth cervical
Spinal Nerve s (C3-C5) in
Humans . It arises from the fifth, sixth and seventh cervical spinal nerves (C5-7) in most
Domestic Animals .
The phrenic nerve is made up mostly of motor nerve fibres for producing contractions of the
Diaphragm . In addition, it provides sensory innervation for many components of the
Mediastinum and
Pleura , as well as the upper abdomen, especially the
Liver and
Gall Bladder .
Both phrenic nerves run from C3, C4 and C5 along the
Anterior Scalene Muscle deep to the
Carotid Sheath .
Both these nerves supply motor fibres to the diaphragm and sensory fibres to the fibrous
Pericardium ,
Mediastinal Pleura and diaphragmatic
Peritoneum .
The
Pericardiacophrenic artery and vein(s) travel with the phrenic nerve.
Pain arising from structures served by the phrenic nerve is often "
Referred " to other somatic regions served by spinal nerves C3-C5. For example, a subphrenic abscess (beneath the diaphragm) might cause a patient to feel pain in the right shoulder.
Irritation of the phrenic nerve (or the tissues supplied by it) leads to the
Hiccup Reflex . A hiccup is a spasmodic contraction of the diaphram, which pulls air against the closed folds of the
Larynx .
The phrenic nerve must be identified during thoracic
Surgery and preserved. It passes anterior to the
Hilum of the corresponding lung, and therefore can be identified easily. Severing the phrenic nerve will paralyse that half of the diaphragm. Breathing will be made more difficult but will continue provided the other nerve is intact.
